/* -*- coding: utf-8 -*-
 *
 * 1876.cc:  No.1876 Xor of Sum - yukicoder
 */

#include<cstdio>
#include<bitset>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 2000;
const int MAX_A = 2000;
const int MAX_M = MAX_N * MAX_A;

/* typedef */

/* global variables */

int as[MAX_N];
bitset<MAX_M+1> dp[2];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", as + i);

  int cur = 0, nxt = 1;
  dp[cur].set(0);

  for (int i = 0; i < n; i++) {
    dp[nxt] = dp[cur] ^ (dp[cur] << as[i]);
    swap(cur, nxt);
  }

  int sum = 0;
  for (int i = 0; i <= MAX_M; i++)
    sum ^= i * dp[cur].test(i);
  printf("%d\n", sum);
  return 0;
}